L-Carnitine protects mammalian cells from chromosome aberrations but not from inhibition of cell proliferation induced by hydrogen peroxide

L-carnitine is a small essential molecule indispensable in fatty acid metabolism and required in several biological pathways regulating cellular homeostasis. Despite considerable progress in understanding of L-carnitine biosynthesis and metabolism, very few data are reported concerning the protective role of L-carnitine from oxidative stress-induced DNA damage that is known to be a factor in cell transformation and tumourigenesis. In order to detect the capability of L-carnitine to protect mammalian cells from oxidative stress-induced chromosomal effects, we analysed chromosome aberrations in mitotic CHO cells, which represent an appropriate cytogenetic model to study compounds that enhance cell protection against externally induced DNA damage. We chose H2O2 as an inducer of oxidative stress. Our results demonstrate for the first time a marked and reproducible reduction of H2O2-induced chromosome damage involving an L-carnitine-mediated capacity to buffer intracellular formation of reactive oxygen species (ROS). Furthermore, by studying the mitotic index and cell cycle progression, we also demonstrated that this protective effect is highly specific, since L-carnitine itself was not able to prevent the inhibition of cell growth caused by H2O2.     

Dissection of human tropoelastin: supramolecular organization of polypeptide sequences coded by particular exons.

Polypeptide sequences encoded by some exons of the human tropoelastin gene (EDP, elastin-derived peptide) have been analysed for their ability to coacervate and to self-assembly. The great majority of them were shown to form organized structures, but only a few were indeed able to coacervate. Negative staining and rotary shadowing transmission electron microscopy showed the polypeptides to adopt a variety of supramolecular organization, from filaments, as those typical of tropoelastin, to amyloid-like fibers. The results obtained gave significant insight to the possible roles played by specific polypeptide sequences of tropoelastin.     

Fourier Transform Infrared Microspectroscopy Detects Changes in Protein Secondary Structure Associated with Desiccation Tolerance in Developing Maize Embryos

Isolated immature maize (Zea mays L.) embryos have been shown to acquire tolerance to rapid drying between 22 and 25 d after pollination (DAP) and to slow drying from 18 DAP onward. To investigate adaptations in protein profile in association with the acquisition of desiccation tolerance in isolated, immature maize embryos, we applied in situ Fourier transform infrared microspectroscopy. In fresh, viable, 20- and 25-DAP embryo axes, the shapes of the different amide-I bands were identical, and this was maintained after flash drying. On rapid drying, the 20-DAP axes had a reduced relative proportion of α-helical protein structure and lost viability. Rapidly dried 25-DAP embryos germinated (74%) and had a protein profile similar to the fresh control axes. On slow drying, the α-helical contribution in both the 20- and 25-DAP embryo axes increased compared with that in the fresh control axes, and survival of desiccation was high. The protein profile in dry, mature axes resembled that after slow drying of the immature axes. Rapid drying resulted in an almost complete loss of membrane integrity in the 20-DAP embryo axes and much less so in the 25-DAP axes. After slow drying, low plasma membrane permeability ensued in both the 20- and 25-DAP axes. We conclude that slow drying of excised, immature embryos leads to an increased proportion of α-helical protein structures in their axes, which coincides with additional tolerance of desiccation stress.     

Moisture content of the dried leaf is critical to desiccation tolerance in detached leaves of the resurrection plant Boea hygroscopica

In our experimental conditions detached leaves of the resurrection plant Boea hygroscopica survived equilibration to 65–80% RH (Relative Humidity), but not to very low RH (close to 0%). The first aim of our research was to determine whether sensitivity to equilibration to very low RH depends on the rate of the drying process or on the very low final MC (Moisture Content) attained. The second aim of our research was to determine ABA content of leaves exposed to the two drying processes: a first step towards understanding whether ABA is involved in the tolerance mechanism of Boea hygroscopica.Detached leaves were equilibrated either to 1.4 or to 60–70% RH or to various temporal combinations of these two RH. ABA content was monitored during drying. Dehydrated leaves were imbibed in liquid water either directly or after a slow rehydration at 98% RH. Tolerance was assessed after 48 h imbibition in liquid water.The low final MC attained (about 3%) and not the rate of drying was responsible of the sensitivity of leaves equilibrated to 1.4% RH. Slow rehydration attained better recovery, but it was not able to allow full resurrection thus suggesting that a plain biophysical liquid-crystalline to gel phase transition of the membrane lipid bilayer could not fully account for the lethal damage of the very low MC.The conclusions relative to the first part of our research was of primary importance in interpreting results concerning ABA variations during the two drying treatments. ABA showed a very similar transient increase when excised leaves were dried at either 1.4% RH (sensitive leaves) or at 60–70% RH (tolerant leaves). However we cannot exclude that the transient increase of the hormone is a necessary component of the desiccation tolerance mechanisms in detached leaves of Boea hygroscopica: the extremely low MC reached by equilibration to 1.4% RH may impair the mechanism itself.     

Effects of different dietary amounts of LCPUFA n3 and vitamin B6 on lipid composition and antioxidant defences in rat kidney

Our previous report demonstrated that, when vitamin deficiency is associated with high contents of long chain polyunsaturated fatty acids (LCPUFA) n3, lipid peroxidation susceptibility in rat heart and liver increases. In this paper, we evaluated the effect of the same dietary administration on lipid composition and antioxidant defenses of rat kidney. Results showed that vitamin B(6) deficiency, when associated with a fish oil diet, as compared to vegetable oil condition, increased relative kidney weight and decreased pyridoxal-5P contents. The different LCPUFA n3 dietary contents produced, on kidney phospholipids, effects interlaced with those of vitamin B(6) deficiency; in particular fish oil and vitamin B(6) deficient diet caused a significant decrease of arachidonic acid showing that the processes of elongation and desaturation of linoleic acid were slowed. Also, peroxidation susceptibility was higher, as demonstrated both by increased TBARS formation and glutathione peroxidase activity, and by decreased vitamin E contents and reduced glutathione/oxidized glutathione ratio.     

Diversity of lactic acid bacteria of the bioethanol process

Background  

Bacteria may compete with yeast for nutrients during bioethanol production process, potentially causing economic losses. This is the first study aiming at the quantification and identification of Lactic Acid Bacteria (LAB) present in the bioethanol industrial processes in different distilleries of Brazil.     

Changes in cell wall composition associated with maturation in the gymnosperm Araucaria angustifolia

A general structural characterization and an investigation on the dynamics of formation of cell wall polysaccharides was performed, using plantlets stem samples from a typical gymnosperm from southern Brazil, Araucaria angustifolia, as experimental model. Microscopic examination and monosaccharide composition of plantlet segments at different heights were carried out to show the representative portions of stem cell wall development. The plantlets were divided in portions (tip, middle and base) which were submitted to sequential extractions. The extraction with water gave rise to large amounts of pectic material in the three portions and more highly substituted pectins occurred in the tip portion of the stems. Increase in alkali concentration extracted, respectively, higher amounts of xyloglucan structurally similar to those from dicotyledons. However, oligosaccharides containing galactose and fucose where found in higher amounts in base than tip portion. The changes in cell wall composition suggest that the development in gymnosperm cell walls follow the same key events as found in dicotyledon walls (type I).     

Terpenoids and phenol derivatives from Malva silvestris

A sesquiterpene and a tetrahydroxylated acyclic diterpene as well as two known monoterpenes, 6 C(13)nor-terpenes and 11 aromatic compounds were isolated from the water extract of Malva silvestris. The structures of the compounds were determined by spectroscopic NMR and MS analysis. Effects of these compounds on germination and growth of dicotyledon Lactuca sativa L. (lettuce) were studied in the 10(-4)-10(-7)M concentration range.     

Investigating by circular dichroism some amyloidogenic elastin-derived polypeptides

Tamburro and coworkers have demonstrated that some elastin-derived polypeptide sequences are able to give rise, in vitro, to amyloid-like fibers. The biological relevance of this finding could be explained by the recent detection of some amyloidogenic material found in arteries of old patients affected by atherosclerosis and demonstrated to be elastin derived. In this context, the comprehension of the mechanism responsible for the amyloid-like fibrillogenesis of elastin-derived sequences is of crucial importance for the design of drugs that could inhibit the amyloidogenic process. To gain further insights into the elastin amyloidogenic process, we studied the polypeptide sequences encoded by Exon 7 and Exon 32 of the human tropoelastin gene, and we demonstrated that only Exon 32 is able to aggregate in amyloid-like fibers. Vis-UV Thioflavin T circular dichroism (CD) spectroscopy rapidly and unambiguously detected the amyloidogenic propensity of the polypeptides. To gain additional insights into the aggregation mechanism of elastin-derived amyloidogenic peptides, we carried out the kinetics of EX32 amyloid-like aggregates by using ThT dye. CD spectroscopy was also used for investigating the secondary structure of the polypeptides, thus giving useful insights into the conformations involved in amyloid-like fiber formation. Furthermore, complementary techniques such as fluorescence spectroscopy, spectral shift, and binding Congo red UV assays as well as atomic force microscopy were also used to confirm the amyloidogenic behavior of the studied polypeptides.     

Effect of chemical cross-linking on the mechanical properties of elastomeric peptides studied by single molecule force spectroscopy

Mechanical properties of animal tissues are mainly provided by the assembly of single elastomeric proteins into a complex network of filaments. Even if the overall elastic properties of such a reticulated structure depend on the mechanical characteristics of the constituents, it is not the only aspect to be considered. In addition, the aggregation mechanism has to be clarified to attain a full knowledge of the molecular basis of the elastic properties of natural nanostructured materials. This aim is even more crucial in the process of rational design of biomaterials with selected mechanical properties, in which not only the mechanics of single molecules but also of their assemblies has to be cared of. In this study, this aspect was approached by means of single molecule stretching experiments. In particular, the effect of chemical cross-linking on the mechanical properties of a naturally inspired elastomeric peptide was investigated. Accordingly, we observed that, in order to preserve the elastic properties of the single filament, the two strands of the dimer have to interact with each other. The results thus confirm that the influence of the aggregation process on the mechanical properties of a molecular assembly cannot be neglected.